This invention relates to an apparatus for the preparation of blood smear specimens, suitable for the formation of stained films of blood on the surface of glass slides for the microscopic observation of blood corpuscles.
In diagnosing a disease, it is a common practice to submit a blood sample from the patient to a test to determine such factors as the form and distribution of white blood corpuscles and red blood corpuscles in the blood sample. This test is effected by a procedure comprising the steps of spreading the blood sample in a thin film on the surface of a glass slide to produce a blood smear specimen, staining the blood smear specimen as required, and observing the stained blood smear through a microscope to determine the form and distribution of the blood corpuscles.
As typical mechanical methods available for the application of blood smears to the surface of glass slides, there have been known the spinner method (U.S. Pat. No. 3,705,048, for example,) and the wedge method. In the spinner method the application of the blood smear is effected by placing the blood sample on a glass slide and spinning the glass slide around the center of the slide thereby causing the sample blood to be centrifugally dispersed into a film on the slide surface. To produce a blood smear in a film of uniform thickness on the surface of a glass slide, by the spinner method the amount of blood sample placed on the glass slide must be so large that some excess blood flies away from the slide surface during spinning. This method, thus requires a large blood sample (generally more than 100 times the amount of blood actually applied to the blood smear) and calls for the extra step of safely disposing of the excess blood spun of the slide. It further entails the problem of possible deformation, destruction, etc. of the blood corpuscles due to the centrifugal force applied thereto during the spinning of the slide.
The wedge method disclosed in Japanese Utility Model Disclosure No. 31545/1977 has resulted from the mechanization of a method heretofore performed by a manual procedure comprising the steps of placing a given blood sample on the surface of a glass slide and then causing a cover glass provided on the glass slide to be moved relative to the glass slide so that one of the longitudinal edges thereof will spread the blood into a thin film on the surface of the glass slide. According to this method, however, since part of the blood used in each application of blood smear remains on the cover glass at the end of the application, the remaining blood must be removed from the cover glass before the cover glass is put to use in the next blood smear application. This method, therefore, has necessitated the extra work of removing the remaining blood from the cover glass by wiping the cover glass with a wad of cotton impregnated with methanol or some other suitable alcohol each time the application of a blood smear is carried out. Thorough removal of the remaining blood by this wiping work has proved to be difficult. Moreover, there is a possibility that proteins and fats originating in various blood samples will accumulate and adhere to the longitudinal edge of the cover glass even to a point where the cover glass will fail to retain the longitudinal edge in a condition appropriate for the preparation of blood smear specimens.
In view of the problems inherent in known methods for preparation of blood smear specimens, it is one object of this invention to provide an apparatus for the preparation of blood smear specimens free from the effects of blood remaining from previous blood application and from the effects of adhesion of proteins and fats.
Another object of this invention is to provide an apparatus for speedy preparation of blood smear specimens wherein blood samples are smeared substantially uniformly.